1. H. Kramers and W. Heisenberg, Z. Phys.,31, 681 (1925).
2. M. Gavrila, Phys. Rev.,163, 147 (1967).
3. S. I. Vetchinkin and S. V. Khristenko, Opt. Spektrosk.,25, 650 (1968); B. A. Zon, N. L. Manakov, and L. P. Rapoport, Zh. Eksp. Teor. Fiz., 55, 924 (1968); Ya. I. Granovskii, Zh. Eksp. Teor. Fiz.,56, 605 (1969).
4. A. Barut, W. Rasmussen, and S. Salamo, Phys. Rev.,D 10, 622 (1974).
5. Coherent States in Quantum Theory, [Russian translation], Mir (1972).